Frequency filter



Feb. 26, 1929. 1,703,184

- 4 e. VON ARco FREQUENCY FILTER Filed Oct. 18, 1923 avwmwoz GEORG VON ARCO his, Elk 0 044 v M XW Patented Feb. 26, 1929.

UNITEDSTATES PATENT OFFICE.

GEORG VON ARGO, OF BERLIN, GERMANY, ASSIGNOR TO GESELLSCHAFT F'U'R DRA.HT'

LOSE TELEGRAPHIE M. B. 11., OF BERLIN,

GERMANY.

Application filed October 18, 1923, Serial No.

Frequency filter arrangements usually comprise a series or chain of electric circuits of certain damping, tuned tothe same frequency and connected to one another by a certain coeflicient of coupling. Although a single circuit; exhibits a resonance-effect only for one particular frequency, such anarrangement of circuits allows a bandof different frequencies to pass about equally well through it.

without attenuation including an electron The breadth of this band depends on the co efiicient of coupling between the circuits of the chain; I f

When electric energy passes through such a frequency filter a loss of energy is unavoidable. The object of the present invention is to couple the circuit of a chain filter by means of amplifying tubes'and to compensate by these tubes this loss of energy, so that the energy is scarcely decreased.

The sin le fi ure of the drawin is a diagrainmatic representation of a circuit arrangement embodying the invention.

The circuits 10, 12, 14 and 16 of the chain shown in the drawing are coupled by amplifying tubes 18, 20 and 22. The degree. of coupling between the input and output circuits of vacuum tubes is normally too low to allow a range of frequencies of sufiicient breadth to pass through the filter. The coefiicient of coupling can, hewever, be increased in a known manner by using a coupling-reaction of one circuit across the tube on the previous circuit, for example, by the use of coupling condensers 24, but this inthe absence of preventative means might give rise to the disadvantage of causing permanent oscillations to be produced by the tube.

According to the invention, the above-mentioned disadvantage is avoided by detuning the circuits 10, 12, 14 and 16 of the chain with relation to each other, preferably in accord ance with a regular order which may vary within wide limits. i

The time-constant of the whole arrangement is decreased by the coupling reaction,-

GERMANY, A CORPORATION 01' FREQUENCY FILTER.

669,234, and in Germany November 16, 1922.

on the one hand, and on the other by'tlie detuning, and this is one of the most important advantages of a frequency filter comprising a chain of circuits coupled by vacuum tubes 'n comparison with the loosely coupled selection-circuits heretofore known.

Having described my invention, what I claim is: i

1. A band filter to pass desired frequencies discharge tube coupled to a syntonizable input circuit'tuned to one desired frequency and asyntonizable output circuit tuned to a different desired frequency, and additional means coupling said output and" input circuits. I

2. A band filter to pass a desired band of frequencies without attenuation including an electron discharge tube coupled to a syntonizable input circuit tuned to one extreme of the desired frequency band, anda syntonizable output circuit tuned to the other extreme of the desired frequency band, and an external capacitance connected between the plate and the grid of said electron discharge tube.

3. In a frequency filter. a plurality of circuits detuned to each other according to a predeterm-inedilaw, means .for coupling con secutive circuits together including an electron discharge tube, and means for additionally coupling an output circuit of said tube to its input circuit to provide'a coupling reaction in order to'obtain a shorter time constant.

4. A frequency 'filter comprising, a plurality of circuits, each circuit tuned to substantially a single frequency only, coupling means for coupling consecutive circuits together, each coupling means including an electron discharge amplifier tube, said tube and its associated circuits being regenerative- 1y coupled, said circuits being detuned to each other to prevent said tube from generating sustained oscillations.

GEORG GRAF vonARCO. 

